I would like to speak of the least healthy aspect of this game.
Said aspect being AD, but more specifically ranged AD's who're easily the largest problems in the game. So overpowered that trying to play a game without one on your side is basically a guaranteed loss. Yet despite that, they feel horrible to play, because if you manage something it's generally effortless, and if you're not able to perform there's very little you can do to fix that. This stems from an inherently horrible bit of design that, while not unique to them, is prevalent throughout them. Quite simply, they are a ranged class with absolutely no counterplay due to a high range, low cooldown, targeted, zero cost ability known as the autoattack being their primary source of damage.
Melee champions avoid this pitfall by being melee. Melee, in and of itself, encourages counterplay because at any given point in time wherein you're getting hit by a melee attack, you're capable of doing something no matter who you're playing. Sometimes, sure, that something may essentially be flailing around helplessly because you shouldn't have gotten into that situation to begin with, but you'll always be able to try and CC them, or kill them, or have your team kill them if they're nearby, or what have you. With a melee champion, there's never nothing you can do, and outplaying them involves manipulating the situation so that the only time they're close enough to hit you is when they're weak enough for you to take them.
Mages, on the other hand, are better. In general, they have the ever impressive ability to miss, which pretty instantly creates a situation wherein there's a high amount of counterplay. On one hand, the mage could heavily outplay you, landing every single one of its abilities and killing you without a care in the world. On the other, you could heavily outplay the mage, avoid basically every single one of their abilities, get close enough, and wreck them without a care in the world. Wherein melee champions are more a case of exploiting openings, mages play a game of prediction where there's a large difference between the best and worst case scenarios, with most situations falling somewhere in the middle. If at any point a mage is ahead, they feel strong, but you'll generally feel that there's still a lot you can do against them if you play well. Wherein if the mage is behind, they feel weak, but there's still a lot that they can do if they play well. Which makes them feel exceptionally rewarding to play with and against. You'll generally never feel hopeless, and the same will generally go for your opposition.
But then there's the ranged AD, which doesn't really have to care about any of that. When you're playing against a ranged AD, there's really no guarantee that you'll be able to do anything about it. Unlike with melee champions, they're sitting pretty in the back row without a care in the world, and they don't have to be close enough to you for you to do anything. And unlike with mages, they can't miss. There is no variance between the best and worst case scenarios. Which leads to an exceptionally binary circumstance. Either you're capable of taking the ranged AD out, either by simply outdoing their range with gapclosers and stomping them into the ground whilst they can't do anything, tanking their hits like they're nothing to the point where they can't do anything, or.... Well, playing a well designed mage and making the world a better place, but we can't all play mages. Or you're incapable of taking the ranged AD out. Because you lack the prowess to instantly close the gap and murder them, and you're not durable enough to make any difference. If you can kill them, it usually sucks to be the ranged AD, because there's basically nothing they can do about it. If you can't kill them, it usually sucks to be you, because there's nothing you can do about it.
And then there are mages. AP master race what what!
Basically, a reliance on ranged autoattacks is the worst mechanic in the game. Outside of Rengar's everything. The simplest and best way to make the game better would be to outright eradicate the focus on any champion utilizing autoattacks or any other 300+ ranged non-gap closing ability. Gap closers, by their nature, are different and would require their own discussion. First and foremost among the methods to do that would be to simply erase crit and every stat that goes along with it. Crit is, bar none, the worst designed stat in the game. Second would be to rework attack speed and CDR, combining the two. One of the major focuses of the game are towers, so you'll never really be able to get rid of attack speed, so instead you should just combine the two stats that function as a "Let me do more damage more often" sort of thing. The combined stat should work on the attack speed system, however, not the CDR one which is plainly inferior.
And then over time reduce the AD in any given sources and increase the AD ratios on champion abilities, until such a time where there are no champions who're primarily autoattackers, and AD simply exists a stat that allows your autoattacks to exist as a supplement. Yes, this would require the reworking of multiple champions. It would most definitely be worth the time spent.